Canonical Question

Antiarrhythmic

V5 D7.iv Historical V4 G7.iii 1 appearance

Master answer

CLASS	ACTION	ELECTRO- PHYSIOLOGY	DRUGS	THERAPEUTIC INDICATIONS
I. Na – Channel Blockers
Ia	Intermediate dissociation	↓ phase 0 ↓↓ conduction v ↑ repolarisation ↑ APD	Quinidine Disopyramide Procainamide	Atrial and ventricular arrhythmias esp. post MI
Ib	Fast dissociation	↔,↓ phase 0 ↓ conduction v ↓ repolarisation ↓ APD	lignocaine phenytoin tocainide, mexilitine	Ventricular arrhythmias post MI, digoxin induced arrhythmias
Ic	Slow dissociation	↓↓↓↓ phase 0 ↓↓↓↓ conduction v ± repolarisation ↔ APD	flecainide ecainide, lorcainide	Refractory arrhythmias
II. β – Blockers
		↓ SA firing – ↓ rate, conduction	propranalol^* atenolol, esmolol	Rate control in AF, AT, Flutter and VT
III. K – Channel Blockers
		Delay phase 3 (repol) ↑ APD ↑ ERP	amiodarone bretylium, sotalol^{^}	AF / Flutter termination
IV. Ca – Channel Blockers
		↓ AV conduction ↑ PR interval ↓ rate/conduction	verapamil diltiazem	SVT and AF or Flutter
OTHERS (Some call this Class V)
	Blocks Na⁺/K⁺ _ATPase→ ↑Ca2⁺, ↓K⁺, ↑Ach	↑ contractility ↓ AV conduction	Digoxin	AF rate control Heart Failure
	Opens K⁺ channels via adenosine receptors	Hyperpolarizes myocardium ↓ AV conduction ↓ SA firing	Adenosine^# Ibutilide	Terminate SVT or reveal underlying rhythm in tachycardias
	Stimulates Na⁺/K⁺_ATPase	Membrane stabilization	Magnesium	VF / Torsades de pointes

Notes		* Propranalol also has Na blocking activity ^ l-sotalol has beta blocking and class III activities; d-sotalol is a pure class III agent. Commercially available sotalol is a racemic (equal part) mixture. # Amiodarone – blocks Na, Ca, K channels, and exhibits beta blockade.

Gladwin / Sakurai / JC 2020

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Answer by Gladwin, JC, Sakurai

Exam appearances

Exam	Exact wording	Relationship	Success
2023A Q11	Outline the Vaughan Williams classification of anti-arhythmic drugs with examples (30% of Marks). Describe the relevant pharmacology of adenosine (70% of Marks)	historical_member	—